Apparatus and method for detecting radiation

ABSTRACT

An apparatus and method for detecting radiation, which can improve the resolution of a radiation image and contribute to the simplification of the manufacture of the apparatus, are provided. The apparatus includes an upper electrode layer transmitting radiation; a first photoconductive layer becoming photoconductive upon exposure to the radiation and thus generating charges therein; a charge trapping layer trapping therein the charges generated in the first photoconductive layer; a second photoconductive layer becoming photoconductive upon exposure to rear light for reading out a radiation image; a lower transparent electrode layer charged with the charges trapped in the charge trapping layer; a micro lens layer disposed between the lower transparent electrode layer and a rear light emission unit and including a plurality of micro lenses respectively corresponding to a plurality of pixels; and the rear light emission unit applying the rear light to the second photoconductive layer via the micro lens layer and the lower transparent electrode layer in units of the pixels.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. §119(a) of KoreanPatent Application No. 10-2010-0095574, filed on Sep. 30, 2010, in theKorean Intellectual Property Office, the entire disclosure of which isincorporated herein by reference for all purposes.

BACKGROUND

1. Field

The following description relates to an apparatus and method fordetecting radiation, which can detect radiation such as X-rays and canthus generate image data

2. Description of the Related Art

Digital radiation detection apparatuses are devices that obtaininformation on the inside of the human body through X-ray irradiationwithout a requirement of films, detect electric image signals from theobtained information with the use of image detection sensors andgenerate a digital image based on the electrical image signals. Digitalradiation detection apparatuses are largely classified into direct-typeand indirect-type digital radiation detection apparatuses. Direct-typedigital radiation detection apparatuses directly detect electric signalsgenerated by irradiating the human body using amorphous selenium (a-Se)and thin film transistors (TFTs). Indirect-type digital radiationdetection apparatuses use light receptors such as charge-coupled deices(CCDs) or photodiodes and thus obtain radiation images from lightemitted by phosphors (such as CsI) that convert radiation into visiblelight. Indirect-type digital radiation detection apparatuses have arelatively low resolution, compared to direct-type digital radiationdetection apparatuses.

Conventional radiation detection apparatuses using TFTs are likely toresult in a considerable amount of noise. The greater the size ofradiation detection apparatuses, the greater the amount of noisegenerated, and the lower the detective quantum efficiency. In addition,since a TFT is required for each pixel in a panel, radiation detectionapparatuses are generally difficult and costly to manufacture on a largescale.

SUMMARY

The following description relates to an apparatus and method fordetecting radiation, which can improve the resolution of radiationimages and can contribute to the simplification of the manufacture ofthe apparatus.

In one general aspect, there is provided an apparatus for detectingradiation, the apparatus including an upper electrode layer transmittingradiation; a first photoconductive layer is becoming photoconductiveupon exposure to the radiation and thus generating charges therein; acharge trapping layer trapping therein the charges generated in thefirst photoconductive layer; a second photoconductive layer becomingphotoconductive upon exposure to rear light for reading out a radiationimage; a lower transparent electrode layer charged with the chargestrapped in the charge trapping layer; a micro lens layer disposedbetween the lower transparent electrode layer and a rear light emissionunit and including a plurality of micro lenses respectivelycorresponding to a plurality of pixels; and the rear light emission unitapplying the rear light to the second photoconductive layer via themicro lens layer and the lower transparent electrode layer in units ofthe pixels.

In another general aspect, there is provided an apparatus for detectingradiation, the apparatus including an upper electrode layer transmittingradiation; a first photoconductive layer becoming photoconductive uponexposure to the radiation and thus generating charges therein; a chargetrapping layer trapping therein the charges generated in the firstphotoconductive layer; a second photoconductive layer becomingphotoconductive upon exposure to rear light for reading out a radiationimage and including a plurality of barrier ribs therein, the barrierribs defining a plurality of pixel regions in the second photoconductivelayer; a lower transparent electrode layer charged with the chargestrapped in the charge trapping layer; and a rear light emission unitapplying the rear light to the second photoconductive layer via thelower transparent electrode layer in units of the pixels.

Other features and aspects may be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an example apparatus for detectingradiation;

FIG. 2 is a circuit diagram for explaining the operation of first andsecond photoconductive layers shown in FIG. 1;

FIG. 3 is a cross-sectional view of another example apparatus fordetecting radiation, which uses light emitted from a plasma displaypanel (PDP) as rear light;

FIGS. 4A through 4E are cross-sectional views for explaining theoperation of another example apparatus for detecting radiation, whichincludes a metal layer as a charge trapping layer;

FIGS. 5A through 5D are cross-sectional views for explaining theoperation of another example apparatus for detecting radiation, whichincludes a dielectric layer as a charge trapping layer;

FIGS. 6A through 6D are cross-sectional views for explaining theoperation of another example apparatus for detecting radiation, whichincludes the combination of a metal layer and a dielectric layer as acharge trapping layer;

FIG. 7 is a flowchart of an example method of detecting radiation;

FIG. 8 is a cross-sectional view of another example apparatus fordetecting radiation; and

FIG. 9 is a cross-sectional view of another example apparatus fordetecting radiation.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following description is provided to assist the reader in gaining acomprehensive understanding of the methods, apparatuses, and/or systemsdescribed herein. Accordingly, various changes, modifications, andequivalents of the methods, apparatuses, and/or systems described hereinwill be suggested to those of ordinary skill in the art. Also,descriptions of well-known functions and constructions may be omittedfor increased clarity and conciseness.

FIG. 1 is a cross-sectional view of an example apparatus 10 fordetecting radiation. Referring to FIG. 1, the apparatus 10 may includean upper electrode layer 101, a first photoconductive layer 102, acharge trapping layer 103, a second photoconductive layer 104, a lowertransparent electrode layer 105 and a data processing unit 200. Theupper electrode layer 101 may transmit radiation incident thereupon froman external source to the first photoconductive layer 102. Examples ofthe radiation include, but are not limited to X-rays, alpha rays andgamma rays.

The first photoconductive layer 102 may become photoconductive uponexposure to the radiation transmitted thereto by the upper electrodelayer 101. That is, the first photoconductive layer 102 may generatepairs of positive and negative charges (i.e., holes and electrons) uponexposure to radiation. The amount of charges generated by the firstphotoconductive layer 102 may be proportional to the intensity ofradiation transmitted to the first photoconductive layer 102. The amountof radiation that reaches the first photoconductive layer 102 may varyaccording to the composition of an object (such as the human body), ifany, placed on the upper electrode layer 101. The first photoconductivelayer 102 may be formed of amorphous selenium (a-Se), As₂Se₃ or anasbestos (As)-contained a-Se compound.

The charge trapping layer 103 may trap therein the positive and negativecharges generated in the first photoconductive layer 102, and may thusserve as a floating electrode. More specifically, the charge trappinglayer 103 may block the charges collected from the first photoconductivelayer 102 and accumulated between the first photoconductive layer 102and the charge trapping layer 103. The charge trapping layer 103 mayinclude a metal layer, a dielectric layer or the combination thereof.

The second photoconductive layer 104 may become photoconductive uponexposure to rear light for reading out a radiation image. The secondphotoconductive layer 104 may generate pairs of positive and negativecharges upon exposure to rear light. The amount of positive and negativecharges generated in the second photoconductive layer 104 may beproportional to the intensity of rear light transmitted to the secondphotoconductive layer 104. The second photoconductive layer 124 may beformed of a-Se, As₂Se₃ or an As-contained a-Se compound.

The term ‘rear light,’ as used herein, indicates light irradiated froman opposite side of the apparatus 10 with respect to the direction ofradiation. Examples of a rear light source include, but are not limitedto, various light source systems capable of applying light in units ofpixels, such as a liquid crystal display (LCD), a plasma display panel(PDP), a light-emitting diode (LED), a field emission display (FED), anda laser light source.

The lower transparent electrode layer 105 may be charged with thecharges trapped in the charge trapping layer 103. The lower transparentelectrode layer 105 may be formed of a transparent material and may thusbe able to transmit rear light therethrough to the secondphotoconductive layer 104. More specifically, the lower transparentelectrode layer 105 may be formed of a transparent material such asindium tin oxide (ITO) or indium zinc oxide (IZO). Once pairs ofpositive and negative charges are generated in the secondphotoconductive layer 104, the lower transparent electrode layer 105 maybe charged with the opposite polarity to that of the charges trapped inthe charge trapping layer 103.

The data processing unit 200 may read out a signal corresponding to thecharges in the lower transparent electrode layer 105 and may thusgenerate a radiation image. FIG. 1 illustrates the structure of aportion of the apparatus 10 corresponding to a pixel. Thus, the dataprocessing unit 200 may perform the reading out of the signal in unitsof pixels or rows or columns of pixels in a pixel array in the apparatus10 and may thus obtain a whole radiation image.

FIG. 2 is a circuit diagram for explaining the operation of the firstand second photoconductive layers 102 and 104, which are stacked withthe charge trapping layer 103 interposed therebetween. Referring to FIG.2, when radiation is transmitted to the first photoconductive layer 102by the upper electrode layer 101, pairs of positive and negative chargesmay be generated in the first photoconductive layer 102. An electricfield may be generated in the upper electrode layer 101 in response to ahigh voltage of, for example, 4 kV, applied to the upper electrode layer101. Then, the positive and negative charges in the firstphotoconductive layer 102 may move toward opposite directions. As aresult, positive or negative charges may be trapped in the chargetrapping layer 103. More specifically, if a negative voltage is appliedto the upper electrode layer 101, the positive charges in the firstphotoconductive layer 102 may move toward the upper electrode layer 101,whereas the negative charges in the photoconductive layer 102 may movetoward the charge trapping layer 103.

Referring to FIG. 2, the first and second photoconductive layers 102 and104, which are stacked with the charge trapping layer 103 interposedtherebetween, may serve as capacitors connected in series. Therelationship between capacitance C and energy W may be defined by thefollowing equation: W=½CV². Since a charge quantity Q₁ of the firstphotoconductive layer 102 is the same as a charge quantity Q₂ of thesecond photoconductive layer 104, ½C₁V₁ ²=½C₂V₂ ² where C₁ and C₂respectively indicate the capacitances of the first and secondphotoconductive layers 102 and 104, and V₁ and V₂ respectively indicatethe voltages of the first and second photoconductive layers 102 and 104.In addition, since

$C = {ɛ_{o}\frac{A}{d}}$

and V=Ed, ½∈_(o)AE₁ ²d₁=½∈_(o)AE₂ ²d₂ where d₁ and d₂ respectivelyindicate the thicknesses of the first and second photoconductive layers102 and 104 and E₁ and E₂ respectively indicate the electric fieldsapplied to the first and second photoconductive layers 102 and 104. Thethickness d₁ of the first photoconductive layer 102 may be much greaterthan the thickness d₂ of the second photoconductive layer 104. Forexample, the thickness d₂ of the first photoconductive layer 102 may beabout 500 μm, and the thickness d₂ of the second photoconductive layer104 may be about 7-12 μm. Thus, the magnitude of the electric field E₂applied to the second photoconductive layer 104 may be greater than themagnitude of the electric field E₁ applied to the second photoconductivelayer 102. During an image recording operation, a high voltage may beapplied to the upper electrode layer 101, whereas, during a radiationimage read-out operation, a ground voltage may be applied to the upperelectrode layer 101. Therefore, most of the electric field generated inthe apparatus 10 may be applied to the second photoconductive layer 104.

Referring to FIG. 2, the charges (regardless of whether positive ornegative) generated in the first photoconductive layer 102 may beblocked by an energy barrier between the charge trapping layer 103 andthe first photoconductive layer 102. Even when blocked by the chargetrapping layer 103, electrons can jump over the energy barrier if theenergy barrier becomes low is due to, for example, a variation in theelectric field or temperature outside the charge trapping layer 103.However, since the electric field applied to the first photoconductivelayer 102 is much weaker than the electric field applied to the secondphotoconductive layer 104, there is no sufficient external energy forthe charges generated in the first photoconductive layer 102 to jumpover the energy barrier. Thus, the charges generated in the firstphotoconductive layer 102 can be effectively blocked by the chargetrapping layer 103.

If rear light is applied to the second photoconductive layer 104 whenthe negative charges are blocked by the charge trapping layer 103, pairsof positive and negative charges may be generated in the secondphotoconductive layer 104. In this case, the positive charges in thesecond photoconductive layer 104 may move toward the charge trappinglayer 103, and thus, the surface of the charge trapping layer 103 may beelectrically neutralized. The negative charges in the secondphotoconductive layer 104 may move toward the lower transparentelectrode layer 105 and may thus be subjected to a radiation imageread-out operation. In short, the negative charges trapped in the chargetrapping layer 103 may be read out, and image processing may beperformed on the read-out negative charges, thereby obtaining aradiation image.

The energy band at the interface between the charge trapping layer 103and the first photoconductive layer 102 may depend on the differencebetween the work function of a conductive material of the chargetrapping layer 103 and the work function of the first photoconductivelayer 102, and may be adjusted according to the physical properties ofthe charge trapping layer 103 and the first photoconductive layer 102such as thickness and specific resistance.

In order to properly trap charges in the charge trapping layer uponexposure to radiation, the charge trapping layer 103 may be formed as ametal layer, a dielectric layer or the combination thereof. Morespecifically, the charge trapping layer 103 may be formed as a is metallayer by using silver (Ag), copper (Cu), gold (Au), aluminum (Al),calcium (Ca), tungsten (W), zinc (Zn), nickel (Ni), iron (Fe), platinum(Pt), tin (Sn), lead (Pb), manganese (Mn), constantan, mercury (Hg),nichrome, carbon (C), germanium (Ge), silicon (Si), glass, quartz,polyethylene terephtalate (PET), or Teflon. Alternatively, the chargetrapping layer 123 may be formed as a dielectric layer by using anorganic dielectric material such as benzocyclobutene (BCB), parylene,a-C:H(F), polyimide (PI), polyarylene ether, or fluorinated amorphouscarbon, an inorganic dielectric material such as SiO₂, Si₃N₄,polysilsequioxane, or methyl silane, or a porous dielectric materialsuch as xetogel/aerogel or polycaprolactone (PCL). By forming the chargetrapping layer 103 as a metal layer, a dielectric layer or thecombination thereof, it is possible to simplify the fabrication of thecharge trapping layer 103, effectively trap the charges generated in thefirst photoconductive layer 102 in the charge trapping layer 103 andreduce the time and cost required to manufacture the apparatus 10,compared to the case when the charge trapping layer 103 is formed ofdoped semiconductor.

FIG. 3 is a cross-sectional view of another example apparatus 20 fordetecting radiation, which uses a plasma display panel (PDP). Referringto FIG. 3, the apparatus 20 may include an upper electrode layer 101, afirst photoconductive layer 102, a charge trapping layer 103, a secondphotoconductive layer 104, a lower transparent electrode layer 105, anintermediate substrate 106 and a PDP 110. The PDP 110, the lowertransparent electrode layer 105, the second photoconductive layer 104,the charge trapping layer 103, the first photoconductive layer 102, andthe upper electrode layer 101 may be sequentially stacked. Theintermediate substrate 106 may support the upper electrode layer 101,the first photoconductive layer 102, the charge trapping layer 103, thesecond photoconductive layer 104 and the lower transparent electrodelayer 105, and may be formed of, for example, glass.

The upper electrode layer 101, the first photoconductive layer 102, thecharge trapping is layer 103, the second photoconductive layer 104, andthe lower transparent electrode layer 105 are the same as theirrespective counterparts shown in FIG. 1, and thus, detailed descriptionsthereof will be omitted.

The PDP 110 may provide plasma light as rear light. The PDP 110 mayinclude a first substrate 111, a plurality of barrier ribs 112, a gaslayer 113, a plurality of phosphor layers 114, an insulating layer 115,a plurality of electrodes 116 and a second substrate 117.

The first and second substrates 111 and 112 may face each other.

The barrier ribs 112 may define a cell structure between the first andsecond substrates 111 and 112. More specifically, the barrier ribs 112may be formed between the first substrate 111 and the insulating layer115 and may thus form a sealed cell structure. The barrier ribs 112 maydefine a plurality of pixels of the PDP 110. The barrier ribs 112 mayprevent crosstalk between the pixels. The barrier ribs 112 may be formedin various shapes such as 2-, 6-, and 8-directional shapes according tothe shape of pixels. The barrier ribs 112 may determine the resolutionof the PDP 110. The barrier ribs 112 may be formed using the same methodused to manufacture a typical PDP. The area and height of the barrierribs 112 can be appropriately adjusted in order to increase the reactionarea of each pixel for radiation.

The gas layer 113 may be disposed in an inner chamber within the cellstructure formed by each of the barrier ribs 112, and may generate aplasma discharge. Plasma light generated by the gas layer 113 may beprovided to the lower transparent electrode layer 105.

The phosphor layers 114 may reflect plasma light generated by the gaslayer 113 and may thus enable high-intensity plasma light to be providedto the lower transparent electrode layer 105. The phosphor layers 114may be formed between the insulating layer 115 and the barrier ribs 112.The phosphor layers 114 may be optional.

The insulating layer 115 may be formed on the second substrate 117 as adielectric layer. The insulating layer 115 may prevent the electrodes116, which are arranged in units of pixels, from being short-circuitedand may also prevent a leakage current. The electrodes 116 may transmitpower for generating plasma to the gas layer 113.

FIGS. 4A through 4E are cross-sectional views for explaining an exampleof the operation of another example apparatus 20 for detectingradiation, which includes a metal layer 103-1 as a charge trappinglayer. The apparatus 30 may be the same as the apparatus 20 shown inFIG. 3 except that it includes the metal layer 103-1 formed of a metal.In FIGS. 4A through 4E, the plus sign ‘+’ indicates a positive charge,and the negative sign ‘−’ indicates a negative charge.

Referring to FIG. 4A, when radiation such as X-rays is applied to theapparatus 30, the radiation may be transmitted to a firstphotoconductive layer 102 through an upper electrode layer 101, andpairs of positive and negative charges may be generated in the firstphotoconductive layer 102. When a high voltage HV is applied to theupper electrode layer 101, the positive and negative charges may beseparated from each other and may move toward opposite directions. Morespecifically, if a negative voltage is applied to the firstphotoconductive layer 102, the positive charges in the firstphotoconductive layer 102 may move toward the upper electrode layer 101,and the negative charges in the first photoconductive layer 102 may movetoward the metal layer 103-1.

The negative charges moving toward the metal layer 103-1 may be trappedin the metal layer 103-1. That is, the negative charges generated in thefirst photoconductive layer 102 may move toward the metal layer 103-1and may thus accumulate at the interface between the firstphotoconductive layer 102 and the metal layer 103-1. The negativecharges accumulated between the first photoconductive layer 102 and themetal layer 103-1 can be blocked by a weak electric field applied to thefirst photoconductive layer 102, as described above with reference toFIG. 2. Since the amount of radiation transmitted through an object(such as the human body), if any, placed on the apparatus 30 variesaccording to the composition and shape of the object, the amount ofpositive and negative charges generated in the first photoconductivelayer 102 and the amount of negative charges trapped in the metal layer103-1 may also vary according to the composition and shape of theobject. Therefore, the amount of negative charges trapped in the metallayer 103-1 may correspond to a radiation image recorded by theapparatus 30.

Once negative charges are trapped in the metal layer 103-1, a secondphotoconductive layer 104 can serve as a capacitor. As a result,referring to FIG. 4B, a lower transparent electrode layer 105 may becharged with positive charges. More specifically, the lower transparentelectrode layer 105 may be charged with a number of positive chargescorresponding to the number of negative charges trapped in the metallayer 103-1.

A radiation image read-out operation will hereinafter be described indetail. If a first row of pixels in the pixel array of a PDP 110 isturned on, plasma light may be emitted from the first row of pixels. Theplasma light may transmit through the lower transparent electrode layer105, and may thus reach the second photoconductive layer 104.

Due to the plasma light, pairs of positive and negative charges may begenerated in the second photoconductive layer 104, and particularly, ina portion of the second photoconductive layer 104 corresponding to thefirst row of pixels. Referring to FIG. 4C, the positive charges in thesecond photoconductive layer 104 may be electrically attracted to thenegative charges trapped in the metal layer 103-1, and the negativecharges in the second photoconductive layer 104 may be electricallyattracted to the positive charges in the lower transparent electrodelayer 105. As a result, the positive and negative charges in the secondphotoconductive layer 104 may be separated from each other.

Thereafter, referring to FIG. 4D, due to the positive charges in thelower transparent electrode layer 105, the negative charges generated bythe second photoconductive layer 104 may be read out from the first rowof pixels by a data processing unit 200. Then, the read-out negativecharges may be subjected to image processing performed by the dataprocessing unit 200.

The positive charges generated in the second photoconductive layer 104may move toward the metal layer 103-1 due to the negative chargestrapped in the metal layer 103-1, and thus, the metal layer 103-1 may beelectrically neutralized.

Thereafter, referring to FIG. 4E, the first row of pixels may be turnedoff, and a second row of pixels may be turned on. Then, the second rowof pixels may emit plasma light. Due to the plasma light, pairs ofpositive and negative charges may be generated in a portion of thesecond photoconductive layer 104 corresponding to the second row ofpixels. The positive and negative charges generated in the secondphotoconductive layer 104 may be electrically attracted to the metallayer 103-1 and the lower transparent electrode layer 105, respectively,and may thus be separated from each other. Due to the positive chargesin the lower transparent electrode layer 105, negative charges may beread out from the portion of the second photoconductive layer 104corresponding to the second row of pixels by the data processing unit200. Then, the read-out negative charges may be subjected to imageprocessing performed by the data processing unit 200.

Thereafter, the same operation as that performed on the first and secondrows of pixels may also be performed on a third row of pixels. As aresult, negative charges may be read out from a portion of the secondphotoconductive layer 104 corresponding to the third row of pixels bythe data processing unit 200. Then, the read-out negative charges may besubjected to image processing performed by the data processing unit 200.

By performing the above-mentioned operation on all rows of pixels in thePDP 110, it is possible to obtain a radiation image of an object, ifany, placed on the apparatus 30.

FIGS. 5A through 5D are cross-sectional views for explaining theoperation of another example apparatus 40 for detecting radiation, whichincludes a dielectric layer 103-2 as a charge trapping layer. Theapparatus 40 is the same as the apparatus 20 shown in FIG. 3 except thatit includes the dielectric material 103-2 as a charge trapping layer.

Referring to FIG. 5A, when radiation such as X-rays is applied to theapparatus 40, the radiation may be transmitted to a firstphotoconductive layer 102 through an upper electrode layer 101, andpairs of positive and negative charges may be generated in the firstphotoconductive layer 102. When a high voltage HV is applied to theupper electrode layer 101, the positive and negative charges may beseparated from each other and may move toward opposite directions. Morespecifically, if a negative voltage is applied to the firstphotoconductive layer 102, the positive charges in the firstphotoconductive layer 102 may move toward the upper electrode layer 101,and the negative charges in the first photoconductive layer 102 may movetoward the dielectric layer 103-2.

Due to the movement of the negative charges toward the dielectric layer103-2, the dielectric layer 103-2 may be polarized, and dipoles may begenerated in the dielectric layer 103-2. The dipoles in the dielectriclayer 103-2 may be arranged in a manner shown in FIG. 5B.

Due to the pattern of the arrangement of the dipoles in the dielectriclayer 103-2, a lower transparent electrode layer 105 may be charged withpositive charges, and particularly, as many positive charges as thereare dipoles in the dielectric layer 103-2.

An image read-out operation will hereinafter be described in detail.

The upper electrode layer 101 may be connected to a ground source. Then,if a first row of pixels in a PDP 110 is turned on, plasma light may beemitted from the first row of pixels. The plasma light may transmitthrough the lower transparent electrode layer 105 and may thus reach asecond photoconductive layer 104.

Referring to FIG. 5C, pairs of positive and negative charges may begenerated in the second photoconductive layer 104, and particularly, ina portion of the second photoconductive layer 104 corresponding to thefirst row of pixels, upon exposure to the plasma light emitted from thefirst row of pixels. The positive and negative charges generated in thesecond photoconductive layer 104 may be electrically attracted to thedielectric layer 103-2 and the lower transparent electrode layer 105,respectively, and may thus be separated from each other.

Referring to FIG. 5D, due to the positive charges in the lowertransparent electrode layer 105, negative charges may be read out fromthe portion of the second photoconductive layer 104 corresponding to thefirst row of pixels by the data processing unit 200. Then, the read-outnegative charges may be subjected to image processing performed by thedata processing unit 200. The positive charges generated in the secondphotoconductive layer 104 may move toward the dielectric layer 103-2 dueto the dipoles in the dielectric layer 103-2.

Thereafter, the first row of pixels may be turned off, and a second rowof pixels may be turned on. Then, the second row of pixels may emitplasma light. Due to the plasma light, pairs of positive and negativecharges may be generated in a portion of the second photoconductivelayer 104 corresponding to the second row of pixels. The positive andnegative charges generated in the second photoconductive layer 104 maybe electrically attracted to the metal layer 103-1 and the lowertransparent electrode layer 105, respectively, and may thus be separatedfrom each other. Due to the positive charges in the lower transparentelectrode layer 105, negative charges may be read out from the portionof the second photoconductive layer 104 corresponding to the second rowof pixels by the data processing unit 200. Then, the read-out negativecharges may be subjected to image processing performed by the dataprocessing unit 200.

Thereafter, the same operation as that performed on the first and secondrows of pixels may also be performed on a third row of pixels. As aresult, negative charges may be read out from a portion of the secondphotoconductive layer 104 corresponding to the third row of pixels bythe data processing unit 200. Then, the read-out negative charges may besubjected to image processing performed by the data processing unit 200.

By performing the above-mentioned operation on all rows of pixels in thePDP 110, it is possible to obtain a radiation image of an object, ifany, placed on the apparatus 40.

FIGS. 6A through 6D are cross-sectional views for explaining theoperation of another example apparatus 50 for detecting radiation, whichincludes both a metal layer 103-2 and a dielectric layer 103-2 thatserve together as a charge trapping layer. The apparatus 50 is the sameas the apparatus 20 shown in FIG. 3 except that it includes the metallayer 103-1 and the dielectric material 103-2 as a charge trappinglayer.

Referring to FIG. 6A, when radiation such as X-rays is applied to theapparatus 50, the radiation may be transmitted to a firstphotoconductive layer 102 through an upper electrode layer 101, andpairs of positive and negative charges may be generated in the firstphotoconductive layer 102. When a high voltage HV is applied to theupper electrode layer 101, the positive and negative charges may beseparated from each other and may move toward opposite directions. Morespecifically, if a negative voltage is applied to the firstphotoconductive layer 102, the positive charges in the firstphotoconductive layer 102 may move toward the upper electrode layer 101,and the negative charges in the first photoconductive layer 102 may movetoward the dielectric layer 103-2.

Due to the movement of the negative charges toward the dielectric layer103-2, the dielectric layer 103-2 may be polarized, and dipoles may begenerated in the dielectric layer 103-2. The dipoles in the dielectriclayer 103-2 may be arranged in a manner shown in FIG. 6B.

Due to the pattern of the arrangement of the dipoles in the dielectriclayer 103-2, the metal layer 103-1 may be charged with positive charges.A lower transparent electrode layer 105 may be charged with negativecharges due to the positive charges in the metal layer 103-1. Morespecifically, the lower transparent electrode layer 105 may be chargedwith as many negative charges as there are dipoles in the dielectriclayer 103-2.

A radiation image read-out operation will hereinafter be described indetail.

The upper electrode layer 101 may be connected to a ground source. Then,if a first row of pixels in a PDP 110 is turned on, plasma light may beemitted from the first row of pixels. The plasma light may transmitthrough the lower transparent electrode layer 105 and may thus reach asecond photoconductive layer 104.

Referring to FIG. 6C, pairs of positive and negative charges may begenerated in the second photoconductive layer 104, and particularly, ina portion of the second photoconductive layer 104 corresponding to thefirst row of pixels, upon exposure to the plasma light emitted from thefirst row of pixels. The positive and negative charges generated in thesecond photoconductive layer 104 may be electrically attracted to themetal layer 103-1 and the lower transparent electrode layer 105,respectively, and may thus be separated from each other.

Referring to FIG. 6D, due to the negative charges in the lowertransparent electrode layer 105, positive charges may be read out fromthe portion of the second photoconductive layer 104 corresponding to thefirst row of pixels by the data processing unit 200. Then, the read-outpositive charges may be subjected to image processing performed by thedata processing unit 200.

Thereafter, the first row of pixels may be turned off, and a second rowof pixels may be turned on. Then, the second row of pixels may emitplasma light. Due to the plasma light, pairs of positive and negativecharges may be generated in a portion of the second photoconductivelayer 104 corresponding to the second row of pixels. The positive andnegative charges generated in the second photoconductive layer 104 maybe electrically attracted to the metal layer 103-1 and the lowertransparent electrode layer 105, respectively, and may thus be separatedfrom each other. Due to the negative charges in the lower transparentelectrode layer 105, positive charges may be read out from the portionof the second photoconductive layer 104 corresponding to the second rowof pixels by the data processing unit 200. Then, the read-out positivecharges may be subjected to image processing performed by the dataprocessing unit 200.

Thereafter, the same operation as that performed on the first and secondrows of pixels may also be performed on a third row of pixels. As aresult, positive charges may be read out from a portion of the secondphotoconductive layer 104 corresponding to the third row of pixels bythe data processing unit 200. Then, the read-out positive charges may besubjected to image processing performed by the data processing unit 200.

By performing the above-mentioned operation on all rows of pixels in thePDP 110, it is possible to obtain a radiation image of an object, ifany, placed on the apparatus 50.

FIG. 7 is a flowchart of an example method of detecting radiation.Referring to FIG. 7, a high voltage may be applied to the upperelectrode layer 101 (710), and radiation may be applied onto the upperelectrode layer 101 (720). Pairs of positive and negative charges may begenerated in the first photoconductive layer 102 (730). The positive andnegative charges may be separated from each other and may move towardthe upper electrode layer 101 and the charge trapping layer 103,respectively. As a result, either the positive or negative charges mayaccumulate in the charge trapping layer 103 (740). More specifically, ifa negative voltage is applied to the upper electrode layer 101, negativecharges may be trapped in the charge trapping layer 103, and thus, thelower transparent electrode layer 105 may be charged with the oppositepolarity to that of the charges trapped in the charge trapping layer103.

The application of a high voltage to the upper electrode layer may beterminated, and the upper electrode layer 101 may be connected to aground source (750). Thereafter, if rear light such as plasma light isapplied (760), pairs of positive and negative charges may be generatedin the second photoconductive layer 104 (770).

Thereafter, a signal corresponding to the charges trapped in the chargetrapping layer 103 may be read out from the lower transparent electrodelayer 105 due to the positive or negative charges in the secondphotoconductive layer 104 (780). Thereafter, a radiation image may begenerated based on the read-out signal (790).

More specifically, if the charge trapping layer 103 includes adielectric layer, the charge trapping layer 103 may be polarized due tothe positive or negative charges in the first photoconductive layer 102,and thus, dipoles may be generated and arranged in the charge trappinglayer 103. Due to the pattern of the arrangement of the dipoles in thecharge trapping layer 103, the lower transparent electrode layer 105 maybe charged, and thus, the positive or negative charges in the secondphotoconductive layer 104 may be attracted to the lower transparentelectrode layer 105. In this manner, a signal reflecting the arrangementof the dipoles in the charge trapping layer 103 can be read out from thelower transparent electrode layer 105.

Alternatively, if the charge trapping layer 103 includes a dielectriclayer and a metal layer and the dielectric layer and the metal layercontact the first photoconductive layer 102 and the secondphotoconductive layer 104, respectively, the dielectric layer may bepolarized due to the positive or negative charges trapped in the chargetrapping layer 103, and thus, dipoles may be generated and arrangeduniformly in the dielectric layer. The metal layer may be chargedaccording to the pattern of the arrangement of the dipoles in thedielectric layer.

As a result, the lower transparent electrode layer 105 may be chargedwith the opposite polarity to that of the charges in the metal layer,e.g., positive charges. During a radiation image read-out operation,positive charges generated in the second photoconductive layer 104 uponexposure to rear light may be attracted to the lower transparentelectrode layer 105, and thus, a signal reflecting the arrangement ofthe dipoles in the dielectric layer or corresponding to the charges inthe metal layer may be read out from the lower transparent electrodelayer 105.

FIG. 8 is a cross-sectional view of another example apparatus 60 fordetecting radiation. Referring to FIG. 8, the apparatus 60 may includean upper electrode layer 101, a first photoconductive layer 102, acharge trapping layer 103, a second photoconductive layer 104, a lowertransparent electrode layer 105, a micro lens layer 120 and a PDP 110.

The apparatus 60 is the same as the apparatus 20 shown in FIG. 3 exceptthat it further includes the micro lens layer 120, which is disposedbetween the lower transparent electrode layer 105 and the PDP 110,instead of an intermediate substrate. The upper electrode layer 101, thefirst photoconductive layer 102, the charge trapping layer 103, thesecond photoconductive layer 104, the lower transparent electrode layer105, and the PDP 110 may be the same as their respective counterpartsshown in FIG. 3, and thus, detailed descriptions thereof will beomitted.

The micro lens layer 120 may include a plurality of micro lenses 121,which respectively correspond to a plurality of pixels in the PDP 110.The micro lenses 121 may concentrate rear light onto their respectivepixel regions in the second photoconductive layer. The micro lenses 121may include convex lenses.

The charge trapping layer 103 may include a metal layer, a dielectriclayer or the combination thereof.

The operation of the apparatus 60 is similar to the operation of theapparatus 20 shown is in FIG. 3. Referring to FIG. 8, charges generatedin the first photoconductive layer 102 may be trapped in the chargetrapping layer 103, and a radiation image corresponding to the chargestrapped in the charge trapping layer 103 may be recorded. Thereafter, afirst row of pixels in the PDP 110 may be turned on, and may thus emitplasma light. The plasma light may reach the second photoconductivelayer 104 through the micro lens layer 120 and the lower transparentelectrode layer 105 as rear light.

The micro lenses 121 of the micro lens layer 120 can effectivelyconcentrate the rear light emitted from the first row of pixels onto aportion of the second photoconductive layer 104 corresponding to thefirst row of pixels without affecting other rows of pixels in the PDP110. As a result, pairs of positive and negative charges can begenerated only in the portion of the second photoconductive layer 104corresponding to the first row of pixels, and a signal corresponding tothe charges trapped in a portion of the charge trapping layer 103corresponding to the first row of pixels can be effectively read outfrom the lower transparent electrode layer 105. Therefore, it ispossible to reduce noise when generating a radiation image throughpixel-wise scanning, and thus to obtain a high-resolution radiationimage.

FIG. 9 is a cross-sectional view of another example apparatus 70 fordetecting radiation. Referring to FIG. 9, the apparatus 70 may includean upper electrode layer 101, a first photoconductive layer 102, acharge trapping layer 103, a second photoconductive layer 104, a lowertransparent electrode layer 105, an intermediate substrate 106 and a PDP110. The apparatus 70 is the same as the apparatus 20 shown in FIG. 3except that it further includes a plurality of second barrier ribs 131.The upper electrode layer 101, the first photoconductive layer 102, thecharge trapping layer 103, the second photoconductive layer 104, thelower transparent electrode layer 105, and the PDP 110 may be the sameas their respective counterparts shown in FIG. 3, and thus, detaileddescriptions thereof will be omitted.

The second barrier ribs 131 may be formed in the second photoconductivelayer 104, and may define a plurality of pixel regions in the secondphotoconductive layer 104. The second barrier ribs 131 may preventcharges generated inside the pixel regions from leaking and may alsoprevent charges generated outside the pixel regions from infiltratinginto the pixel regions. The second barrier ribs 131 may be formed usingthe same method used to form a plurality of first barrier ribs 112.

The operation of the apparatus 70 is similar to the operation of theapparatus 20 shown in FIG. 3. Referring to FIG. 9, charges generated inthe first photoconductive layer 102 may be trapped in the chargetrapping layer 103, and a radiation image corresponding to the chargestrapped in the charge trapping layer 103 may be recorded. Thereafter, afirst row of pixels in the PDP 110 may be turned on, and may thus emitplasma light. The plasma light may reach the second photoconductivelayer 104 through the lower transparent electrode layer 105 as rearlight. Then, pairs of positive and negative charges may be generatedonly in pixel regions in the second photoconductive layer 104corresponding to the first row of pixels, and a signal corresponding tothe charges trapped in a portion of the charge trapping layer 103corresponding to the first row of pixels can be effectively read outfrom the lower transparent electrode layer 105.

Even if positive and negative charges are generated outside the pixelregions corresponding to the first row of pixels upon exposure to theplasma light, they can be effectively prevented from infiltrating intothe pixel regions corresponding to the first row of pixels by the secondbarrier ribs 131. Thus, the charges only in the pixel regionscorresponding to the first row of pixels can be read out via the lowertransparent electrode layer 104. In addition, the charges generated inthe pixel regions corresponding to the first row of pixels can beprevented from leaking by the second barrier ribs 131. Therefore, it ispossible to reduce noise when generating a radiation image throughpixel-wise scanning, and thus to obtain a high-resolution radiationimage.

As described above, it is possible to provide an apparatus and methodfor detecting radiation, which can improve the resolution of a radiationimage and can contribute to the simplification of the manufacture of theapparatus.

A number of examples have been described above. Nevertheless, it shouldbe understood that various modifications may be made. For example,suitable results may be achieved if the described techniques areperformed in a different order and/or if components in a describedsystem, architecture, device, or circuit are combined in a differentmanner and/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

1. An apparatus for detecting radiation, the apparatus comprising: anupper electrode layer transmitting radiation; a first photoconductivelayer becoming photoconductive upon exposure to the radiation and thusgenerating charges therein; a charge trapping layer trapping therein thecharges generated in the first photoconductive layer; a secondphotoconductive layer becoming photoconductive upon exposure to rearlight for reading out a radiation image; a lower transparent electrodelayer charged with the charges trapped in the charge trapping layer; amicro lens layer disposed between the lower transparent electrode layerand a rear light emission unit and including a plurality of micro lensesrespectively corresponding to a plurality is of pixels; and the rearlight emission unit applying the rear light to the secondphotoconductive layer via the micro lens layer and the lower transparentelectrode layer in units of the pixels.
 2. The apparatus of claim 1,wherein the micro lenses concentrate the rear light so that the rearlight can be applied only onto their respective pixel regions in thesecond photoconductive layer.
 3. The apparatus of claim 1, wherein thecharge trapping layer includes a metal layer.
 4. The apparatus of claim1, wherein the charge trapping layer includes a dielectric layer.
 5. Theapparatus of claim 1, wherein the charge trapping layer includes a metallayer and a dielectric layer.
 6. The apparatus of claim 1, wherein,during the trapping of charges in the charge trapping layer, a highvoltage is applied to the upper electrode layer, and during the readingout of charges from the lower transparent electrode layer, the upperelectrode is connected to a ground source.
 7. The apparatus of claim 1,wherein the rear light emission unit comprises a plasma display panel(PDP) including two substrates facing each other, a plurality of barrierribs defining a cell structure between the two substrates, and a gaslayer disposed in an inner chamber inside the cell structure andemitting plasma light, the PDP providing the plasma light to the lowertransparent electrode layer as the rear light.
 8. The apparatus of claim1, further comprising a data processing unit reading out a signalcorresponding to the charges trapped in the charge trapping layer fromthe lower transparent electrode layer and generating a radiation imagebased on the read-out signal.
 9. An apparatus for detecting radiation,the apparatus comprising: an upper electrode layer transmittingradiation; a first photoconductive layer becoming photoconductive uponexposure to the radiation and thus generating charges therein; a chargetrapping layer trapping therein the charges generated in the firstphotoconductive layer; a second photoconductive layer becomingphotoconductive upon exposure to rear light for reading out a radiationimage and including a plurality of barrier ribs therein, the barrierribs defining a plurality of pixel regions in the second photoconductivelayer; a lower transparent electrode layer charged with the chargestrapped in the charge trapping layer; and a rear light emission unitapplying the rear light to the second photoconductive layer via thelower transparent electrode layer in units of the pixels.
 10. Theapparatus of claim 9, wherein the barrier ribs prevent positive andnegative charges generated inside the pixel regions upon exposure to therear light from leaking and prevent positive and negative chargesgenerated outside the pixel regions upon exposure to the rear light frominfiltrating into the pixel regions.
 11. The apparatus of claim 9,wherein the charge trapping layer includes a metal layer.
 12. Theapparatus of claim 9, wherein the charge trapping layer includes adielectric layer.
 13. The apparatus of claim 9, wherein the chargetrapping layer includes a metal layer and a dielectric layer.
 14. Theapparatus of claim 9, wherein the rear light emission unit comprises aPDP including two substrates facing each other, a plurality of barrierribs defining a cell structure between the two substrates, and a gaslayer disposed in an inner chamber inside the cell structure andemitting plasma light, the PDP providing the plasma light to the lowertransparent electrode layer as the rear light.